U.S. patent number 5,634,263 [Application Number 08/526,341] was granted by the patent office on 1997-06-03 for methods of manufacture of permanent magnet structures with sheet material.
This patent grant is currently assigned to The United States of America as represented by the Secretary of the Army. Invention is credited to Herbert A. Leupold.
United States Patent |
5,634,263 |
Leupold |
June 3, 1997 |
Methods of manufacture of permanent magnet structures with sheet
material
Abstract
Methods of manufacturing relatively complex permanent magnet
structures uizing sheets of permanent magnet material. Different
permanent magnet structures such as rings, cylinders, spheres,
oblate and prolate forms are made from cut or stamped sections of
the sheets of permanent magnet material. In one embodiment,
toroidal sections having a uniform magnetic orientation are cut or
stamped out. The sections are rearranged to form a "magic" ring
having a desirable substantially uniform magnetic field in the
center thereof. In another embodiment, the "magic" rings are
stacked together to form a "magic" cylinder. In another embodiment,
the "magic" rings are divided and beveled to form wedges, slices,
or spheroidal segments that are used to assemble a "magic" sphere
having a central working cavity with a desirable relatively strong
uniform magnetic field. In yet another embodiment, sheets of
permanent magnet material are cut into trapezoidal sections and the
trapezoidal sections arranged to form oblate and prolate permanent
magnet structures that permit relatively distortion free polar and
equatorial access respectively. The present invention, in utilizing
a sheet of permanent magnet material and the stamping of shapes,
makes possible inexpensive and easily mass produced manufacturing
of relatively complex permanent magnet structures. This makes
possible wide spread application of relatively complex permanent
magnet structures having desirable magnetic fields to many known
devices.
Inventors: |
Leupold; Herbert A. (Eatontown,
NJ) |
Assignee: |
The United States of America as
represented by the Secretary of the Army (Washington,
DC)
|
Family
ID: |
24096940 |
Appl.
No.: |
08/526,341 |
Filed: |
September 11, 1995 |
Current U.S.
Class: |
29/607; 29/415;
29/416 |
Current CPC
Class: |
H01F
7/0278 (20130101); Y10T 29/49796 (20150115); Y10T
29/49075 (20150115); Y10T 29/49794 (20150115) |
Current International
Class: |
H01F
7/02 (20060101); H01F 041/02 () |
Field of
Search: |
;29/607,609,602.1,415,416 ;335/306 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Hall; Carl E.
Attorney, Agent or Firm: Zelenka; Michael Anderson; William
H.
Government Interests
GOVERNMENT INTEREST
The invention described herein may be manufactured, used and
licensed by or for the United States Government for governmental
purposes without the payment to me of any royalties thereon.
Claims
What is claimed is:
1. A method of making an oblate permanent magnet structure having a
desired working magnetic field in a working space comprising the
steps of:
magnetizing a plurality of sheets of permanent magnet material in a
predetermined direction;
cutting the plurality of sheets of permanent magnet material having
a magnetic orientation into a plurality of predetermined shapes
such that the magnetic orientation is transverse to the
longitudinal axis of each of said plurality of predetermined
shapes, each of said plurality of sheets having a different width;
and
assembling said plurality of predetermined shapes into an oblate
permanent magnet structure such that the magnetic orientation of
each of said plurality of predetermined shapes is substantially
tangential to the working space containing the desired working
magnetic field.
2. A method of making a permanent magnet structure as in claim 1
wherein:
said plurality of predetermined shapes are trapezoidal.
3. A method of making a prolate permanent magnet structure having a
desired working magnetic field in a working space comprising the
steps of;
magnetizing a plurality of sheets of permanent magnet material in a
predetermined direction;
cutting the plurality of sheets of permanent magnet material having
a magnetic orientation into a plurality of predetermined shapes
such that the magnetic orientation is substantially parallel to the
longitudinal axis of each of said plurality of predetermined
shapes, each of said plurality of sheets having a different width;
and
assembling said plurality of predetermined shapes into a prolate
permanent magnet structure such that the magnetic orientation of
each of said plurality of predetermined shapes extends
substantially radially from a central point in the desired working
space containing the working magnetic field.
4. A method of making a permanent magnet structure as in claim 3
wherein:
said plurality of predetermined shapes are trapezoidal.
Description
FIELD OF THE INVENTION
The present invention relates to the manufacture of permanent
permanent magnet structures, and more particularly to the
manufacture of rings, cylinders, hemispheres, spheres, and other
desired shapes.
BACKGROUND OF THE INVENTION
There are many devices that require a relatively strong, uniform
magnetic field. For example, magnetic resonant imaging devices,
power tubes for radars, and other known devices that utilize a
relatively strong, uniform magnetic field. Many of these permanent
permanent magnet structures provide a relatively high uniform
magnetic field and have embodied the principles of a "magic" ring,
cylinder, hemisphere, or sphere. For example, several permanent
magnet structures of this type are disclosed in U.S. Pat. No.
5,216,401 issuing Jun. 1, 1993 to Leupold and entitled "Magnetic
Field Sources Having Non-Distorting Access Ports", which is herein
incorporated by reference. Therein disclosed is a permanent magnet
structure having a shell of magnetic material and a hollow cavity.
The shell is permanently magnetized to produce a substantially
uniform magnetic field in the cavity. The magnetization of the
shell is the result of two magnetization components. Another
example is U.S. Pat. No. 4,835,506 issuing May 30, 1989 to Leupold
and entitled "Hollow Substantially Hemispherical Permanent Magnet
High Field Flex Source", which is herein incorporated by reference.
Therein disclosed is a hollow hemispherical flex source which
produces a uniform high magnetic field in its central cavity. The
hemispherical permanent magnet structure is comprised of a
plurality of wedge shaped portions having multiple sections with
each section having a defined magnetic orientation.
Additionally, there have been manufacturing methods developed in an
attempt to manufacture more easily these relatively complex
permanent magnet structures. A method of manufacturing a magic ring
or a cylinder is disclosed in U.S. Statutory Invention Registration
H591 published Mar. 7, 1989, issuing to Leupold and entitled
"Method of Manufacturing of a Magic Ring", which is herein
incorporated by reference. Therein disclosed is a method of making
a permanent magnet cylindrical structure made from magnetically
hard material which provides a relatively intense uniform magnetic
field within a central working space. The cylinder is cut into
sections and then opposing pairs of sections are interchanged to
form the desired magnetic orientation. Another method of making
permanent magnet cylindrical and spherical structures is disclosed
in U.S. Pat. No. 5,337,472 issued Aug. 16, 1994 to Leupold and
McLane and entitled "Method of Making Cylindrical and Spherical
Permanent Magnet Structures", which is herein incorporated by
reference. Therein disclosed are methods of manufacturing rings,
cylinders, hemispheres, and spheres having a relatively strong
central magnetic field. A method is disclosed of making a
hemispherical or spherical permanent magnet structure by cutting
wedge or melon shaped portions into sections, rotating the sections
about a radial axis prior to magnetization, magnetizing the
sections in a uniform magnetic field, rotating the magnetic
sections into their original positions, thereby forming the
resultant desired permanent magnet structure. Additionally
disclosed is the method of rearranging sections in order to obtain
a desired magnetic orientation.
While many of these permanent magnet structures are desirable, they
are often difficult to manufacture. Additionally, while the above
described methods facilitate the manufacturing of these relatively
complicated permanent magnet structures, the above methods do not
lend themselves to mass production. Therefore, as these relatively
complex permanent magnet structures become more widely used and
incorporated into more devises, there is a need for developing
manufacturing methods that are suitable for mass production,
including permitting relatively easy and inexpensive manufacture of
these relatively complex permanent magnet structures.
SUMMARY OF THE INVENTION
The present invention relates to a method of manufacturing
permanent permanent magnet structures having substantially uniform
magnetic fields from a sheet of magnetic material. In one
embodiment, toroids or donut shapes are stamped from a sheet of
magnetic material. The toroids are cut into sections. The sections
are arranged into a predetermined magnetic orientation forming a
"magic" ring that has a desired relatively uniform transverse
magnetic field. The "magic" rings may be stacked to form a "magic"
cylinder. In another embodiment, the "magic" rings formed from the
sheet material are beveled to form wedges or slices for forming
spheres, hemispheres, or other spheroidal shapes.
In another embodiment of the present invention, sheets of magnetic
material are cut into trapezoids. The use of different widths of
sheet material for forming trapezoids having different longitudinal
lengths are used to make oblate or prolate permanent magnet
structures permitting relatively distortion-free polar or
equatorial access, respectively.
Accordingly, it is an object of the present invention to provide a
method for mass producing permanent magnet structures having
desirable relatively strong uniform working magnetic fields.
It is another object of the present invention to provide efficient
manufacturing of permanent magnet structures having relatively
complex shapes.
It is an advantage of the present invention that waste is reduced
in the manufacture of desired permanent magnet structures.
It is another advantage of the present invention that relatively
few manufacturing steps are needed to make a desired permanent
magnet structure.
It is a feature of the present invention that relatively
inexpensive, easily fabricated sheet permanent magnet material is
used.
It is another feature of the present invention that the sheet
magnetic material is easily cut and assembled to form the desired,
relatively complex permanent magnet structure.
These and other objects, advantages, and features will become
readily apparent in view of the following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A is a pictorial view of a sheet of permanent magnet
material.
FIG. 1B is a pictorial view of the sheet permanent magnet material
having circles cut therein.
FIG. 1C is a pictorial view illustrating the formation of a
plurality of toroidal shapes.
FIG. 1D is a pictorial view illustrating the cutting into sections
of the plurality of toroidal shapes.
FIG. 1E is a pictorial view illustrating the repositioning of the
sections of one of the plurality of toroidal shapes.
FIG. 1F is a pictorial view illustrating a "magic" ring formed by
the repositioning of the sections in one of the plurality of
toroidal shapes.
FIG. 1G is a perspective view illustrating a plurality of "magic"
rings stacked to form a "magic" cylinder.
FIG. 1H is a top plan view illustrating a "magic" ring.
FIG. 1I is a top plan view illustrating the two spheroidal
segments, wedges, or slices formed from the "magic" ring.
FIG. 1J is a top plan view illustrating the assembly of a plurality
of spheroidal segments, wedges, or slices substantially forming a
sphere.
FIG. 2A is a pictorial view illustrating a sheet of permanent
magnet material.
FIG. 2B is a pictorial view illustrating the cutting of the sheet
of permanent magnet material.
FIG. 2C is a pictorial view illustrating the formation of the
plurality of trapezoids.
FIG. 2D a pictorial view illustrating the formation of an oblate
permanent magnet structure.
FIG. 3A is a pictorial view illustrating a sheet of permanent
magnet material.
FIG. 3B is a pictorial view illustrating the cutting of the sheet
of permanent magnet material into trapezoids.
FIG. 3C is a pictorial view illustrating the formation of a prolate
permanent magnet structure.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1A illustrates a sheet of permanent magnet material 10. The
sheet of permanent magnet material 10 is substantially planar and
has a magnetization parallel to the surface and in a longitudinal
direction. The orientation of the magnetization is illustrated by
arrows 12. The sheet of permanent magnet material 10 is uniformly
magnetized. The sheet of permanent magnet material 10 is made of
any well known current permanent magnet material. The manufacture
of sheets of permanent magnet material 10 are well known and
accomplished relatively easily and inexpensively. From the sheet of
permanent magnet material 10 are cut discs 14. The cutting of discs
14 from the sheet of permanent magnet material 10 may easily and
inexpensively be accomplished by a grinding cutter. FIG. 1C
illustrates the cutting of holes 16 from the plurality of discs 14.
Similarly, the cutting of holes can easily and inexpensively be
accomplished by stamping. FIG. 1D illustrates the plurality of the
toroidal or donut shapes that are easily and inexpensively stamped
out of the sheet of permanent magnet material 10. The toroidal or
donut shaped permanent magnet material 18 is cut along radial lines
20 to form sections 22. The number of sections 22 cut from each of
the plurality of toroidal shapes 18 depends upon the application.
However, in general, the larger the number of sections the more
uniform the resultant working magnetic field will be. By rotating
each section 22 along its radial axis 24 one-half a revolution or
180.degree., as illustrated in FIG. 1E by arrows 26, the desired
magnetic orientation for a "magic" ring 28 is obtained as
illustrated in FIG. 1F. As illustrated in FIG. 1F, the working
magnetic field within bore 16 is relatively strong and in the
direction of large arrow 30. Other methods of repositioning the
sections 22 may be used, such as those disclosed in U.S. Pat. No.
5,337,472 and U.S. Statutory Invention Registration H591 referred
to above. FIG. 1G illustrates the formation of a "magic" cylinder
32. The "magic" cylinder 32 is formed by stacking a plurality of
the "magic" rings 28. In view of the large number of "magic" rings
28, that are required to form a "magic" cylinder 32, the benefits
of using techniques to mass produce permanent magnet structures can
readily be appreciated.
FIGS. 1H, 1I, and 1J illustrate the application of the present
invention to the formation of a spheroidal or spherical shape such
as a hemisphere or a sphere. The toroidal or donut shaped permanent
magnet material 18 is divided in the direction of the magnetic
field along the axial diameter. The two halves are beveled forming
spheroidal portions, slices, or wedge-like, trapezoidal or
spherical segments 34. The axial diameter of division formed at the
apex of the spherical segments 34. The resulting spherical segments
34 rearrange to obtain the desired magnetic orientation and
azimuthally assembled about the axial diameter to form the desired
spheroidal or substantially spherical permanent magnet structure 36
illustrated in FIG. 1J, thereby creating a "magic" sphere having a
desired substantially uniform working magnetic field formed in the
cavity created by bore sections 16.
FIGS. 2A, 2B, 2C, and 2D illustrate the use of a sheet permanent
magnet material 10 in forming a desirable oblate permanent magnet
structure. By oblate permanent magnet structure it is meant that
the radial dimension varies, permitting relatively distortion-free
polar access with the use of a uniformly magnetized permanent
magnet material. FIG. 2A illustrates a sheet of permanent magnet
material 10 having a uniform magnetization represented by arrows
12. The sheet of permanent magnet material 10 is cut into
triangular shaped sections 38. The smallest angle of each
triangular shaped section 38 forms a vortex. The direction of
magnetization represented by arrows 12 of each triangular shaped
section 38 is transverse and preferably perpendicular to the
longitudinal axis of the triangular shaped sections 38. FIG. 2C
illustrates the formation of a plurality of trapezoids 38' by the
cutting of a distance R.sub.i in from each longitudinal edge of the
sheet of permanent magnet material 10. The resulting trapezoids 38'
have a longitudinal length W. The length cut from each longitudinal
end of the sheet of permanent magnet material 10 has a length
R.sub.i equal to the radius of the desired working space having the
working magnetic field of the resultant permanent magnet structure
to be formed. Alternatively, the trapezoidal shapes may be directly
cut from the sheet of permanent magnet material 10. FIG. 2D
illustrates the formation of an oblate permanent magnet structure
using the trapezoidal shaped sections cut from the sheet of
permanent magnet material 10. A different longitudinal length is
used for each of the trapezoidal sections 38a-38e. One each of the
trapezoidal sections 38a-e is used for each quadrant. For the
oblate permanent magnet structure 40 illustrated in FIG. 2D, five
different widths W of sheet permanent magnet material 10 are
needed. The longitudinal length of each trapezoidal section 38a-38e
varies, with the longest longitudinal length located at the equator
and the shortest longitudinal length located near a pole. The
resulting working magnetic field within the and working space or
cavity formed by bore 16' is illustrated by arrow 30. Because the
magnetic orientation, represented by arrows 12, is perpendicular to
the longitudinal or radial axis of each of the trapezoidal sections
38a-38e, the resulting magnetic orientations are substantially
tangential to the edge of the working space or cavity formed by
bore 16'. The number of toroidal sections 38' needed to assemble
the oblate permanent magnet structure 40 is given by the following
formula: ##EQU1## where gamma is the angle, in degrees, subtended
by each trapezoidal section or the angle formed by the vortex. The
angle gamma of the vortex is selected depending upon the position
and fineness of texture of the desired magnetic field. However, the
approximation is very good even for relatively large angles of
gamma. In extreme cases, a small angle gamma may be used resulting
in a large number of trapezoidal sections, and the surfaces may be
ground to more closely conform to an ideal or theoretical exterior
surface curve of the desired oblate permanent magnet structure.
Additionally, the oblate permanent magnet structure 40 illustrated
in FIG. 2D may be in the form of a single ring, a plurality of
rings forming a cylinder, or an assembly of rings that have been
beveled and assembled into a spheroid. The shape of the stamped
sections of permanent magnet 10 are illustrated as being
trapezoidal, however other predetermined shapes may be stamped. For
example, other quadrilateral shapes may be used, or a predetermined
shape that will form the preferred exterior curved surfaces may be
directly cut. This will eliminate the need for cutting or grinding
smooth, if desired, the stepped exterior surfaces that will result
when trapezoidal sections are combined.
FIGS. 3A, 3B, and 3C illustrate the analogous method of
manufacturing a prolate permanent magnet structure. By prolate
permanent magnet structure, it is meant that the radial dimension
is elongated at the poles permitting relatively distortion-free
equatorial access with the use of a uniformly magnetized permanent
magnet material. FIG. 3A illustrates a sheet of permanent magnet
material 110 that has a magnetic orientation illustrated by arrows
112. The magnetic orientation is substantially perpendicular to the
longitudinal axis of the sheet of permanent magnet material 110.
The sheet of permanent magnet material 110 is cut into a plurality
of trapezoidal sections 138. The trapezoidal sections 138 have a
longitudinal length W. The vertex formed by the two longitudinal
sides of the trapezoidal sections 138 form an angle gamma.
Accordingly, the magnetic orientation, represented by arrows 112,
is parallel to the longitudinal axis of the trapezoidal sections
138. As discussed above, the trapezoidal sections 138 may be formed
by the cutting of a triangular section or by directly cutting the
trapezoidal sections 138 from the sheet of permanent magnet
material 110. Additionally, as discussed above, the angle gamma is
selected depending upon the desired properties of the magnetic
field, with the smaller of the angle gamma corresponding to more
closely achieving the ideal or theoretical magnetic field. However,
illustrated in FIG. 3C, the prolate permanent magnet structure 42,
for purposes of example, illustrates five trapezoidal sections
138a-138e each having different a different longitudinal or radial
lengths. One each of the five trapezoidal sections 138a-138e is
used per quadrant. Therefore, for a predetermined width of the
sheet of permanent magnet material 110, four trapezoidal sections
will be used, one for each quadrant. The assembled prolate
permanent magnet structure 42 results in a working cavity or space
formed by bore 116 having a substantially uniform magnetic field in
the direction indicated by arrow 30. As indicated above, in order
to achieve a more uniform or ideal magnetic field, the exterior
surfaces of the trapezoidal sections 138a-138e may be ground to
more closely approximate the desired ideal or theoretical curved
surface. Additionally, as indicated above the other quadrilateral
shapes may be used, or a predetermined shape that will form the
preferred exterior curved surfaces may be directly stamped. The
magnetic orientations, represented by arrows 112, of the
trapezoidal sections 138a-138e are substantially perpendicular to
the surface of the working space or cavity formed by bore 116.
Additionally, as indicated above, the prolate permanent magnet
structure 42 may be made in the form of a ring, cylinder, or
spheroid using the methods as described above.
The present invention, in utilizing relatively inexpensive, easily
produced or manufactured inexpensive sheets of permanent magnet
material, provides a method of manufacturing relatively complex
permanent magnet structures that is readily susceptible to mass
production. Therefore, the present invention reduces the cost and
time required to manufacture known, relatively complex permanent
magnet structures, permitting these permanent magnet structures to
be widely used and made available for numerous known applications
that previously could not be made available due to cost. Therefore,
it should be appreciated that the present invention greatly
advances the art relating to the manufacture of permanent magnet
structures. Additionally, while several embodiments have been
illustrated and described, it will be obvious to those skilled in
the art that various modifications may be made without departing
from the spirit and scope of this invention.
* * * * *